Collapsible Monoplane
The difficulty of carrying a fairly large model to a convenient flying
ground prevents many would-be makers taking a practical interest in
model flying. The necessity of overcoming this difficulty has resulted
in several excellent designs, one of the best being the monoplane
designed and constructed by Mr. A. B. Clark, the secretary of the
South-Eastern Model Aero Club. When this model monoplane was built the
objects aimed at were extreme reliability and easy conveyance to and
from the flying grounds situated some distance away.
The model is fitted with a chassis to enable it to start off good
ground under its own power; but this starting-gear is so constructed
that the whole model will pack up flat and make a convenient parcel. In
fact, the complete model will easily go into a cardboard box measuring
2 ft. 10 in. by 1 ft. 2 in.
Referring to the accompanying illustrations, Fig. 96 shows the plan
view of the complete machine, Fig. 97 a side view, and Fig. 98 a front
view. The body (fuselage) is made of two pieces of silver spruce, 3
ft. 6 in. long, ⅜ in. deep, and ³/₁₆ in. thick. These gradually taper
towards each end, where they measure ¼ in. by ³/₁₆ in. Two distance
pieces of bamboo are shaped to streamline form and placed at equal
distances along the fuselage; the front piece is 2⅜ in., the other 2
in. These pieces should be pointed at the ends, and fit in a slot made
in the side lengths, as indicated at =A= (Fig. 99), and then bound very
tightly with glued narrow silk tape or ribbon, as indicated at =B=.
This is the neatest and also the strongest method of making joints for
model aeroplane frames. The ends of the two long lengths should be
bound together with strong thread and carefully glued.
The tail (used in place of the familiar elevator) is built on to the
rear end of the fuselage, and is composed of two pieces of yellow
bamboo, 9¾ in. by ⁵/₁₆ in by ⅛ in., tapering to ⅛ in. square at the
end to which the propeller bearings are attached. These bearings are
made of No. 18 or No. 20 S.W.G. piano wire, and their shape is clearly
shown in Fig. 100. The bearings are bound to the inner edge of the wood
with glued thread or fine flower wire. The wide ends of the bamboo
lengths are held over a bunsen (the blue flame of an incandescent
burner is very suitable), and bent to the angle shown in Fig. 96. The
trailing edge of the tail is made of No. 26 S.W.G. piano wire, or a G
banjo string. The wire is taken right through the end of the fuselage,
a small hole being carefully drilled ½ in. from the end. A bead of
solder should be run on the wire on both sides of the hole, to prevent
movement in a lateral direction, and the two ends are taken through the
bearings and bound to the bamboo with fine wire, leaving sufficient
to form hooks for the two bracing wires to be afterwards attached.
The whole of this tail framework is covered with proofed silk on both
sides, thus forming an approximate streamline surface, which has proved
remarkably efficient. Two triangular pieces of silk should be cut out,
just large enough to give sufficient overlap. They should be attached
with fish glue, and stretched as tightly as possible.
[Illustration: Fig. 96]
[Illustration: Fig. 97]
[Illustration: Fig. 98]
[Illustration: Fig. 99]
[Illustration: Fig. 100]
[Illustration: Fig. 101
Figs. 96 to 101.—Arrangement and Details of Collapsible Monoplane]
At the other end of the fuselage is attached the hooks for the elastic,
and the wire forming them is also utilised as a protector. The whole
construction is made from a 10½-in. length of No. 18 S.W.G. piano wire,
reinforced with a strip of thin bamboo, bent to shape over a blue flame
and bound with silk tape. The part is shown unbound in Fig. 101, and
Fig. 102 shows an alternative protector; but it is not so effective.
The main plane is made of bamboo and piano wire of No. 18 S.W.G., and
measures 2 ft. 10 in. by 6¼ in. The leading edge is of bamboo 3 ft. 2
in. long, ³/₁₆ in. wide, tapering to ⅛ in. at the ends, with a uniform
thickness of ⅛ in. When planed down the length should be heated over
a blue flame, and bent to the shape shown in Fig. 96, the outside of
the bamboo being kept on the outside of the curve. The trailing edge
should now be attached to the ends of the leading edge, a length of ½
in. being bent up at each end of the wire, and securely bound to the
bamboo. The ribs should now be cut from the same gauge wire. The ends
should be bent out at an angle so that they may be bound to the leading
and trailing edges, as shown in Fig. 103; the projecting ends should be
about ⅜ in.
[Illustration: Fig. 102]
[Illustration: Fig. 103]
[Illustration: Fig. 104]
[Illustration: Fig. 105]
[Illustration: Fig. 106]
[Illustration: Fig. 107]
[Illustration: Fig. 108]
[Illustration: Fig. 109
Figs. 102 to 109. Details of Collapsible Monoplane]
The two centre ribs are shaped as shown in Fig. 104. It will be seen
that the leading edge is raised ¼ in. above the fuselage, and the rear
edge is level with it. The ends of the ribs are fitted into small holes
drilled in the top of the fuselage, and kept in position by means of
small metal clips, as shown in Figs. 105 and 106. Four of the clips are
required, and they may be easily made from thin tinplate and soldered.
The ribs should be soldered to the trailing edge so as to make them
secure. The framework should be covered with proofed silk, and neatly
glued on all edges.
[Illustration: Fig. 110.—Rear Skid]
[Illustration: Fig. 111]
[Illustration: Fig. 112
Figs. 111 and 112.—Details of Screw]
The chassis is shown by Fig. 107, No. 18 gauge piano wire being used
for the framing, and an ordinary cycle spoke for the axle. Figs. 108
and 109 show the flexible joints of the chassis, which folds up flat
when the hooks at =C= (Fig. 107) are withdrawn.
The wheels are 2 in. in diameter, and are rubber tyred, the ends of the
spoke being burred over to keep them in position.
The rear skid is shown in Fig. 110, and is made of No. 18 gauge piano
wire. A single length is used, being bent to shape, passed through the
end of the fuselage, and held to its work by the projecting end =D=,
which fits in a hole in the under-side of one of the pieces of wood.
When not in use the skid may be folded flat.
The two propellers are of the simple bentwood type, 10 in. in diameter
and 1 ft. 8 in. pitch. They are made of ¹/₁₆-in. birch in the usual
way. The shape of the blades is shown in Fig. 111, and the angle at
which the blades are bent is shown in Fig. 112. Six strands of strip
rubber should be attached to each propeller, ordinary soft soap being
used as a lubricant.